rsync - Jul 2005 - multiple daemons on the same port

I thought if a daemon is already running on the default port, I
thought the additional ones started on the same port will result in an
exit with error, but somehow it seems to work just fine. If I kill the
first process, the second process seems to take control of the port.
As far as I know you can't have two processes binding to the same
port, so does that mean the second process is just polling for the
port to be available? This seems very counter-intuitive. Can anyone
explain?

Thanks,
Hari

On 7/31/05, alok barnwal <alokbarnwal2000@yahoo.com>
wrote:
> Hi Hari,
> Your observations is very true.
> And you cannot have 2 processess running on same port.
> Such problem is being faced when you try to restart
> particular service and found that previous instance is
> not properly stopped and hence port was not free when
> new process try to occupy that port.
> Better implementations is that
> 1.Optimise TCP parameters of your system.
> 2.In your daemon script check whether port is free or
> not. if not make it free before starting process.
> 
> Regards
> Alok
It is not clear from your reply, why rsync behaves in this nonstandard
way, and why I should optimize TCP parameters, but I can certainly run
rsync client in list-module mode to see if the daemon is already
running. Of course, I can also open a connection to the port, but
using rsync client will certainly be safer.

--
Thank you,
Hari
> 
> --- Hari Krishna Dara <haridara@gmail.com> wrote:
> 
> > I thought if a daemon is already running on the
> > default port, I
> > thought the additional ones started on the same port
> > will result in an
> > exit with error, but somehow it seems to work just
> > fine. If I kill the
> > first process, the second process seems to take
> > control of the port.
> > As far as I know you can't have two processes
> > binding to the same
> > port, so does that mean the second process is just
> > polling for the
> > port to be available? This seems very
> > counter-intuitive. Can anyone
> > explain?
> >
> > Thanks,
> > Hari

On Fri, Jul 29, 2005 at 06:28:03PM -0700, Hari Krishna Dara
wrote:
> I thought if a daemon is already running on the default port, I
> thought the additional ones started on the same port will result
> in an exit with error
It certainly works that way on all the Unix-like OSes I know.  The
error is output to the rsync log file:

Aug  1 11:11:11 dot rsyncd[111]: unable to bind any inbound sockets on port 873

You're talking about running the "rsync --daemon" command, right?

..wayne..